The present invention relates to a vertical centrifugal hydraulic pump assembly in which the hydraulic interstage pumping assemblies are enclosed in at least one replaceable cartridge or pack constituting a block clamped vertically between two flanged end plates for retaining the pack in the bore of a pump body.
Such vertically-arranged centrifugal pump assemblies in which, for the purposes of repair or replacement of parts, it is possible to simply remove the active hydraulic part of the pump which takes the form of a replaceable pack or cartridge of hydraulic elements consisting of rotors and of stators forming a stack housed in an exchangeable cylindrical block, are widely used. Such assemblies allow very speedy replacement (usually a matter of several minutes) after provisionally removing the electric drive motor of the pump, or simply the active hydraulic part of the pump, this being the part which most frequently suffers from operating problems and problems resulting from wear. Such speedy replacement however requires a preliminary step to be carried out, consisting in isolating the pump with respect to the inlet delivery fluid supply main, which currently is not always possible. Such isolation requires that shut-off cocks be present and the closing of these can turn out to be particularly difficult in the case of units consisting of a plurality of pumps where twin or triple pumps are employed, with a standby pump able to take the place, generally in an automatic manner, of a pump that has failed.
The present invention sets out to make it possible to isolate the replaceable pack that incorporates the hydraulic elements using a simple non-return valve which requires no modification to the design and cost of pump assemblies. The provisions of the invention are particularly advantageous in the case of multiple pumps which are mounted on a single pump housing block.